1. Field of the Invention
The present invention relates to a combination type damper and a washing machine having the same, and more particularly, to a combination type damper capable of minimizing a vibration transmission to other components by effectively absorbing steady state vibration and transient state vibration by using an electromagnetic force and a frictional damping force, and a washing machine having the same.
2. Description of the Conventional Art
Generally, a washing machine washes laundry by performing a washing operation, a rinsing operation, and a dehydration operation. Washing methods of the washing machine include a method for washing laundry accordingly as vortex generated when a washing bar having blades is rotated in the middle of a laundry basin applies an impact to laundry, a method for washing laundry accordingly as vortex generated when a rotation blade mounted at a lower portion of a laundry basin is rotated applies an impact to laundry, a method for washing laundry by an impact that laundry drops by rotating a drum in which laundry is put in a horizontal direction, and etc.
FIG. 1 is a front section view showing one embodiment of a general washing machine.
As shown, the washing machine comprises: a cabinet 100 having an inner space of a predetermined shape; a tub 210 positioned in the cabinet 100; a drum 220 rotatably inserted into the tub 210 and through which laundry is introduced; a driving motor 230 mounted at a rear surface of the tub 210 for rotating the drum 220; a spring 110 mounted between the cabinet 100 and an upper portion of the tub 210 for elastically supporting the tub 210; a damper 300 mounted between the cabinet 100 and a lower portion of the tub 210 for absorbing vibration; a water supply means (not shown) for supplying washing water into the tub 210; a drain means (not shown) for draining water inside the tub 210; and a door (not shown) for opening and closing the drum 220.
The tub 210, the drum 220, and the driving motor 230 constitute one tub assembly 200, and the tub assembly 200 is supported by the damper 300 and the spring 110.
For a washing operation in the washing machine, first, the door is opened thus to put laundry into the drum 220, then the door is closed, and detergent and washing water are put into the drum, thereby rotating the drum 220 by a driving of the driving motor 230. After the washing operation, a rinsing operation is performed and then washing water is drained by the drain means. Then, a dehydration operation that washing water remaining on the laundry is removed by a centrifugal force accordingly as the drum 220 is rotated with a high speed is performed.
In a general washing machine, vibration is generated in the tub assembly at the time of a washing operation or a dehydration operation, and the vibration is absorbed by the spring 110 and the damper 300 thus to be prevented from being transmitted to the cabinet 100.
If vibration generated from the tub assembly 200 is transmitted to the cabinet 100, great vibration noise is generated at the cabinet 100, which causes uncomfortable feeling and degrades a reliability of a product. Accordingly, minimizing vibration noise is a great task.
FIG. 2 is a front section view showing a damper constituting the washing machine by partially cutting. As shown, the damper 300 comprises: a first body 310 having one side relative-movably coupled to the tub 210 and having a frictional surface 311 of a cylindrical shape at an inner portion of another side thereof; a second body 320 having one side relative-movably coupled to the cabinet 100 and having another side inserted into the frictional surface 311 of the first body 310; and a frictional member 330 fixedly coupled to the second body 320 to be in contact with the frictional surface 311 of the first body for generating a frictional force at the time of moving. Also, a guide bush 340 for blocking a gap between the first body 310 and the second body 320 is coupled to an inlet of the frictional surface 311 of the first body 310.
The frictional member 330 is formed of generally grease impregnation sponge with a ring shape having a certain thickness and length, and a coupling groove 321 having a certain depth and length is formed at the outer circumferential surface of the second body 320 at one side thereof. The frictional member 330 is inserted into the coupling groove 321 of the second body. The outer circumferential surface of the frictional member 330 comes into contact with the inner circumferential surface of the first body 310, that is, the frictional surface 311.
In the damper 300, when vibration generated from the tub assembly 200 is transmitted, the first body 310 and the second body 320 perform a relative movement. That is, the second body 320 moves towards a straight line direction and thereby the frictional member 330 is moved together. According to this, a constant friction is generated between the outer circumferential surface of the frictional member 330 and the frictional surface 311 of the first body, thereby absorbing vibration transmitted from the tub assembly 200.
However, in the washing machine, a degree of vibration generated from the tub assembly 200 is different in an entire process for washing laundry. Therefore, by the damper 300 which generates a constant frictional force, steady state vibration and transient state vibration having various widths can not be sufficiently absorbed.
That is, steady state vibration is generated at the time of a dehydration operation of a normal state of a high speed or at the time of a washing operation or a normal state, and transient state vibration is generated in a process for reaching the normal dehydration operation of a high speed or for stopping at the normal high speed dehydration operation. Therefore, even if transient state vibration can be absorbed to some degree by the constant frictional force of the damper, steady state vibration is transmitted to the tub assembly 200 and the cabinet 100 thus to generate vibration noise outwardly.